Geared grip actuation for medical instruments

ABSTRACT

An actuation mechanism for a medical instrument includes a pinion and a face gear that move a push-pull element. The pinion has a mounting that permits rotation of the pinion by an external control system such as a robot. The face gear meshes with the pinion. The push-pull element may have a proximal end coupled to the face gear and a distal end coupled to a tool at a distal end of an instrument shaft. A manipulator coupled for manual rotation of the actuation mechanism may include a slip clutch to prevent manual application of excessive force to the actuation mechanism.

RELATED APPLICATION

This patent application claims priority to and the benefit of the filingdate of U.S. Provisional Patent Application 62/362,365, entitled “GEAREDGRIP ACTUATION FOR MEDICAL INSTRUMENTS” filed Jul. 14, 2016, which isincorporated by reference herein in its entirety.

BACKGROUND

Minimally-invasive medical procedures often employ medical instrumentshaving a tool or end effector or other manipulation element at thedistal end of an elongated instrument shaft. During a minimally-invasivemedical procedure, the distal ends of one or more such medicalinstruments may be inserted through one or more small incisions and/ornatural lumens to position the distal tools at a work site in a patient.A surgeon or other medical personnel may then control the tools toperform desired clinical functions, e.g., endoscopy, laparoscopy,arthroscopy, hypodermic injection, air-pressure injection, subdermalimplants, refractive surgery, percutaneous surgery, cryosurgery,microsurgery, keyhole surgery, endovascular surgery such as angioplasty,coronary catheterization, placement of internal electrodes, andstereotactic surgery, at the work site.

The manipulations required or desired to effectively complete medicalprocedures can be complex and intricate. Accordingly, medicalinstruments for minimally-invasive medical procedures may need toprovide precise control of many degrees of freedom of movement. Onecommon degree of freedom that may be required for a medical instrumentis grip. For example, a surgeon may need an instrument with a distaltool capable holding, moving, clamping, cutting, or cauterizing oftarget tissue, and such distal tool may accordingly need to close (oropen) a grip mechanism such as a clamp or scissors. In a medicalinstrument, the mechanics for actuation of grip may benefit from beingcompact to allow space for other mechanisms that control other degreesof freedom movement of the instrument.

SUMMARY

In accordance with an aspect of the invention, a grip actuationmechanism uses a face gear and pinion to push and pull a grip driveelement.

One specific implementation is a medical system containing an actuationmechanism. An actuation mechanism may include a pinion and a face gearcoupled to move a push-pull element. The pinion has a mounting thatpermits rotation of the pinion by an external control system such as arobot. The face gear meshes with the pinion. The push-pull element mayhave a proximal end coupled to the face gear and a distal end coupled toa tool at a distal end of an instrument shaft. A manipulator coupled formanual rotation of the actuation mechanism may include a slip clutch toprevent manual application of excessive force to the actuationmechanism.

Another specific implementation is a medical instrument including atool, an actuation mechanism, and a manipulator. The actuation mechanismmay be coupled to the tool and may have an engagement feature shaped toengage an actuator in a robot, so that rotation of the engagementfeature actuates a portion of the tool. The manipulator, which couplesto the actuation mechanism so that rotation of the manipulator actuatesa portion of the tool, may include a slip clutch that limits the torquemanually applied to the actuation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a robotic system that can deploy and operate multiplemedical instruments.

FIG. 2A and FIG. 2B respectively show perspective and top views of anexample implementation of a medical instrument.

FIG. 3A shows a perspective view of an example implementation of a gripmechanism.

FIG. 3B shows some components of the grip mechanism of FIG. 3A.

FIG. 4A and FIG. 4B respectively show front and back perspective viewsof an example implementation of an actuation mechanism.

FIG. 4C schematically shows an arrangement of the pinion and face gearused in the actuation mechanism of FIGS. 4A and 4B.

FIG. 5 shows an exploded view of an example implementation of aconnector for connecting an actuation mechanism to push-pull element ina medical instrument.

FIG. 6 shows structure in a backend of an example implementation of amedical instrument containing the actuation mechanism of FIGS. 4A and4B.

FIG. 7A is an exploded view of an example implementation of amanipulator suitable for manual operation of an actuation mechanism andincluding a slip clutch.

FIG. 7B shows a partial cross-sectional view of the manipulator of FIG.7A when assembled.

FIG. 8 shows a partial cross-sectional view of an example implementationof a manipulator with a slip clutch using springs to engage a plungerwith an input drive shaft.

FIGS. 9A and 9B respectively show exploded and cross-sectional views ofan example implementation of a manipulator with a slip clutch usingsprings to engage a plunger with a notched plate.

FIG. 10 shows a cross-sectional view of an example implementation of amanipulator with a slip clutch using clip that is friction fit on aninput drive shaft.

The drawings illustrate examples for the purpose of explanation and arenot of the invention itself. Use of the same reference symbols indifferent figures indicates similar or identical items.

DETAILED DESCRIPTION

An actuation mechanism for an instrument such as a medical instrumentmay include a gear structure including a face gear and a pinion forprecision driving of back-and-forth movement such as grip motion in theinstrument. The face gear and pinion may be relatively simple to mold orcut and may be arranged in a compact configuration that is tolerant ofmisalignment during assembly. The gear structure may also allowflexibility for different arrangement of rotation axes of an instrumentinput and the face gear. The face gear arrangement may further allow fora high gear ratio when driving a grip mechanism and may still providelow driving friction that allows the grip actuation mechanism to be backdriven, i.e., allows the gear structure to move in response to amovement of the grip mechanism.

The grip actuation mechanism may reside in proximal portion of aninstrument such as a medical instrument, sometimes referred to herein asthe backend of the instrument. The grip actuation mechanism mayparticularly connect to an elongated push-pull element having a proximalend coupled to the actuation mechanism and a distal end coupled to agrip mechanism at the distal end of an elongate instrument shaft of aninstrument. In one implementation, the proximal end of the push-pullelement couples to a face gear in the actuation mechanism, and an inputspindle shaped to engage an actuator such as a drive motor in a roboticsystem may include or may be coupled to rotate a pinion that meshes withthe face gear. Rotation of the input spindle rotates the pinion and facegear, which may then push or pull the push-pull element and therebydrive closing or opening of the grip mechanism at the distal end of theinstrument. In this description, the root term robot and its derivativesinclude teleoperated systems that use technology associated withrobotics, such as a mechanically grounded or hand-held teleoperatedsurgical system. In addition, the term manipulator and its derivativesinclude any means—motor or manual—for conveying force or torque to movea mechanical object (manipulator is a term of art in robotics, and inthis description it includes manual equivalents).

The actuation mechanism may further permit manual operation or actuationof grip motion. In particular, users of an instrument such as a medicalinstrument may need to manually open or close the jaws of the instrumentwhen the instrument is in hand instead of being attached to a robotic orother computer-assisted system, and the grip actuation mechanism mayfurther include a manipulator such as a knob, handle, or lever that isconnected for manual rotation of the pinion and opening or closing ofthe jaws. A slip clutch or torque limiter may connect the manipulator tothe pinion. The slip clutch may be particularly desirable when aninstrument includes a push-pull element such as a rod, wire, or cablethat is thin, structurally weak, or runs through relatively weak guide.In such cases, pushing the push-pull element with too much force maycause the push-pull element (with or without a guide) to buckle or kink.While a robotic system may be programmed to monitor and limit the forcethat the robotic system applies to a push-pull element, users of thesystem may not be able to properly judge manually applied forces. Theslip clutch may limit manually applied force to avoid damage and maystill permit manual driving of back-and-forth movement in an instrument.

Although the above examples and other discussions herein often refer tomedical procedures and medical instruments, the techniques disclosedalso apply to non-medical procedures and non-medical instruments.

FIG. 1 shows an example of a medical system 100 using multiple medicalinstruments 110, some or all of which may include a grip actuationmechanism disclosed herein. System 100, which may, for example, includea da Vinci® Surgical System commercialized by Intuitive Surgical, Inc.,and may particularly employ multiple instruments 110, each of which isreplaceable and mounted in a docking port 120 on a manipulator arm 130of a robot 140. A sterile barrier (not shown) including a drape andadaptors for instruments 110 may be between instruments 110 and robot140, so that robot 140, including manipulator arms 130 and docking ports120, is outside a sterile environment for a patient. Accordingly, robot140 may not need to be sterilized between medical procedures. Incontrast, instruments 110, which may be used inside the sterileenvironment and may contact the patient, are compact and removable sothat instruments 110 may be cleaned and sterilized or replaced betweenmedical procedures performed using system 100.

Instruments 110 may vary in structure and purpose but may still beinterchangeable and have a standard engagement interface, so thatdifferent types of instruments 110 may be mounted in docking ports 120of robot 140 as needed for a particular medical procedure. Instruments110 may also be changed during a medical procedure to provide thedifferent clinical functions as needed. Each instrument 110 generallyincludes an end effector or distal tool 112, an elongated instrumentshaft 114, and a backend 116. Distal tools 112 may have differentdesigns to implement many different functions. For example, some distaltools 112 for instruments 110 that may provide grip motion may includeforceps, graspers, scissors, or cautery tools, which may come indifferent shapes or sizes. In general, instruments 110 having differentdistal tools 112 may be mounted on different arms 130 of robot 140 andmay work cooperatively in the same work site, although not all distaltools 112 need to provide gripping action. An endoscopic camera, forexample, a stereoscopic camera, can also be mounted on an arm to providevisual information, particularly images, of the work site in whichdistal tools 112 of instruments 110 may be operating.

Docking ports 120 may include actuators such as drive motors thatprovide mechanical power for actuation of mechanical structures ininstruments 110, drive couplings that connect the actuators to inputs ofinstruments 110, and systems for establishing and maintaining of asterile barrier between instruments 110 and the rest of medical system100. Docking ports 120 may additionally include an electrical interfaceto provide power to instruments 110, e.g., for cautery tools, or forcommunication with instruments 110, e.g., to identify the type ofinstrument 110 in a docking port 120, to access parameters of a dockedinstrument 110, or to receive information from sensors in a dockedinstrument 110. For example, the electrical interface may provide a highfrequency AC voltage that a medical instrument 110 applies to both ofthe jaws in a distal cautery tool for a monopolar cauterization process,or the electrical interface may provide opposite polarity electricalsignals that a medical instrument 110 applies to electrically-isolated,opposing jaws for a bipolar cauterization process. A computer system,which may be connected to or part of robot 140 and connected to a userinterface device (not shown), may receive the information frominstruments 110 and receive user commands from a surgeon or othermedical personnel and may execute software that controls arms 130 andthe actuators in docking ports 120 as needed to mechanically actuate andelectrically power systems in instruments 110 as needed to execute tothe user commands.

FIGS. 2A and 2B respectively illustrate perspective and top views of anexample implementation of a medical instrument 110 suitable for use inmedical system 100 of FIG. 1. As shown in FIG. 2A, medical instrument110 includes a tool 112 at the distal end of an elongated instrumentshaft 114 that extends from a backend 116. Distal tool 112 andinstrument shaft 114 may have multiple degrees of freedom of movementrelative to backend 116, and in the illustrated configuration of FIG.2A, medical instrument 110 has six degrees of freedom corresponding to:two types of actuation of a first joint mechanism 211; two more types ofactuation of a second joint mechanism 212; opening or closing movementof jaws 213; and rotations of instrument shaft 114 about its central orlength axis. First joint mechanism 211 and second joint mechanism 212may also be termed first joint 211 and second joint 212, respectively.In some embodiments, a first wrist comprises first joint 211, and asecond wrist comprises second joint 212. Other implementations ofmedical instruments may provide more, fewer, or different degrees offreedom of movement.

Backend 116 as shown in FIG. 2B has six input spindles 221 to 226 withexterior engagement features that are shaped and positioned to engageactuators in a docking port of a robotic system, e.g., to engage drivemotors in docking ports 120 of robot 140 as shown in FIG. 1. In thisspecific example, first and second actuators in the robot may rotateinput spindles 221 and 222 to control actuation of wrist or joint 211.Third and fourth actuators in the robot may rotate input spindles 223and 224 to control actuation of wrist or joint 212. A fifth actuator mayrotate input spindle 225 to control opening or closing 205 of jaws 213,and a sixth actuator may rotate input spindle 226 to control rollrotation of instrument shaft 114. In accordance with one aspectdisclosed herein, backend 116 includes a grip actuation mechanism thatmay act as a transmission to convert the rotation of input spindle 225into movement that opens or closes jaws 213 or to control a pressurethat jaws 213 may apply when opening or closing. Backend 116 alsoincludes a manipulator 220 that permits manual rotation of input spindle225 for manual control of jaws 213.

FIG. 3A shows an implementation of a distal grip mechanism 300 for oneexample of a distal tool such as distal tool 112 of FIGS. 1, 2A, and 2BAlternatively, any actuated mechanism that requires driving of openingand closing or back-and-forth movement may be similarly employed andactuated as disclosed herein. In the specific example FIGS. 3A and 3B,grip mechanism 300 includes a pair of jaws 310 mounted on an end portion320 of a distal tool or at the distal end of instrument shaft 114 withor without intervening wrist mechanisms such as joints 211 or 212 shownin FIG. 2A. Jaws 310 may include a first jaw member 325 and a second jawmember 327 configured to move between an open position and a closedposition. Each jaw member may have a range of motion from about 0degrees to about 30 degrees, providing a full range of motion for thejaws 310 from about 0 degrees to about 60 degrees. A grip angle θ asshown in FIG. 3B may be defined as the angle between faces of the jawmembers 325 and 327. When jaw members 325 and 327 are touching oneanother, such that the faces of both jaw members extend along centerline350, the grip angle θ is approximately 0 degrees, and the jaws are in aclosed position. When the jaw members are fully spaced away from oneanother, the jaws are in a fully open position, and the grip angle θ maybe approximately 60 degrees. This range of “grip motion” is intended tobe exemplary only, and the range of grip motion in differentimplementations of a grip mechanism can be larger or smaller based uponthe intended use of the instrument and may depend upon the structure ofthe jaw members, the manner of connection of the jaw members, and/or themanner of actuation of the jaw members.

FIG. 3B shows how each jaw member 325 or 327 may include a proximalextension 329 or 331, and FIG. 3A shows proximal extensions 329 and 331mounted in a clevis 335. In some embodiments, proximal extensions 329and 331 may each comprise a jaw extension. Clevis 335 supports gripmechanism 300 and connects grip mechanism 300 to adjacent portion 320 ofthe medical instrument, e.g., as jaws 213 connect to wrist mechanisms212 and 211 and instrument shaft 114 as shown in FIG. 2A. In theimplementation of FIGS. 3A and 3B, a clevis pin 345 extends throughholes 340 in the sides of clevis 335 and through holes 325 a and 327 ain proximal extensions 329 and 331 to pivotally couple jaw members 325and 327 to clevis 335, permitting the jaws to open and close as theypivot about pin 345. In addition, proximal extensions 329 and 331 mayinclude respective cam slots 325 b and 327 b through which a pin 337moves during the opening and closing of the jaws 310. Pin 337particularly connects to and moves with a push-pull element 360 thatextends from pin 337 and through the instrument shaft to connect to agrip actuation mechanism in the backend of the medical instrument.Push-pull element 360 may include one or more sections of a relativelyrigid structure such as a rod and one or more sections of a moreflexible structure such as a cable or wire in a guide or sheath 365 thatsupports and guides push-pull element 360. A flexible section ofpush-pull element 360 with guide or sheath 365 may allow driven openingand closing grip mechanism 300 even when push-pull element 360 must beable to flex or bend, for example, where element 360 passes throughactuated joints 211 or 212 of FIG. 2A. In operation, a grip actuationmechanism in the backend of a medical instrument connects to push-pullelement 360 and may push or pull push-pull element 360 to cause jaws 310to open or close.

FIGS. 4A and 4B show front and back perspective views of oneimplementation of an actuation mechanism 400, which includes a face gear410 and an input gear or pinion 420. Face gear 410 has a shaft 412 thatdefines a rotation axis of face gear 410 and may ride in bearingsmounted in or on the chassis of the instrument backend containing gripactuation mechanism 400. Face gear 410 may particularly be mounted on achassis in a manner that permits back-and-forth rotation of face gear410 over a limited angular range about shaft 412. Face gear 410 may be asector gear with a toothed portion 414 that only subtends a limitedangle, e.g., about 32 degrees, depending on the desired range of motionof face gear 410. A connector 430 attaches push-pull element 360 to facegear 410, so that the small angle rocking motion of face gear 410primarily moves push-pull element 360 along a length axis of theinstrument shaft through which push-pull element 360 passes. In general,the diameter of face gear 410 and the moment arm relative to shaft 412at which connector 430 attaches to face gear 410 may be selected ordesigned to provide a desired range of motion of push-pull element 360and provide a desired gear ratio or mechanical advantage when pinion 420acts on face gear 410.

Pinion 420 meshes with toothed portion 414 on a front side of pinion420, and a support bearing 440 as shown in FIG. 4B may be used on a backside of pinion 420 and opposing input pinion 420 to ensure that teeth ofgears 410 and 420 remain engaged even under high loads. Pinion 420 maybe mounted on or otherwise coupled to input spindle 225 so that pinion420 rotates when a control system rotates input spindle 225. Inparticular, input spindle 225 includes an engagement feature 425 shapedto engage an actuator, e.g., a drive motor, in an instrument dockingport of a robotic system, so that the robotic system may operate theactuator to rotate input spindle 225 and pinion 420 to control movementof push-pull element 360 and to thereby control opening and closing of agrip mechanism attached to push-pull element 360. A manipulator 220,e.g., a knob, handle, lever, or other structure capable of beingmanually turned, also connects to pinion 420 so that a user can manuallyrotate manipulator 220 and pinion 420 to move face gear 410 andpush-pull element 360 and manually open or close the distal gripmechanism, e.g., grip mechanism 300 of FIG. 3A. As described furtherbelow, a slip clutch or torque limiter may connect manipulator 220 topinion 420 or input spindle 225 to limit the maximum torque or forcethat a user can manually apply for at least one direction of motion,e.g., for pushing, of push-pull element 360.

Pinion 420 in the implementation shown in FIG. 4A is a helical gear, iscylindrical, and meshes with a flat toothed portion 414 of face gear 410so that rotation axes of gears 410 and 420 do not intersect. FIG. 4Cschematically illustrates the positions of face gear 410 and pinion 420of mechanism 400 without other obscuring elements. As shown, a rotationaxis of pinion 420 may be offset by a distance X1 from the rotation axisand shaft 412 of face gear 410. The helix angle of pinion 420 may beselected according to the tooth pattern of face gear 410, offset X1, anda desired skew between the rotation axes 412 and 422 of face gear 410and pinion 420. Alternative gear configurations or actuation mechanismsmay use the same principles but vary offset X1 and the helix angleaccording to the space available for the actuation mechanism. Further,pinion 420 may be a cylindrical spur gear and tooth portion 414 of facegear 410 may be shaped to accommodate a spur gear as pinion 420. Instill other implementations, gears 410 and 420 may be bevel gears.However, implementations in which pinion 420 is a cylindrical spur or ahelical gear acting on a flat face gear 410 have the advantage oftolerance for vertical misalignment of input pinion 420 relative to facegear 410. Specifically, axial misalignment or shifting of pinion 420along rotation axis 422 does not affect gear performance of actuationmechanism 400, which makes actuation mechanism 400 reliable and easy toassemble. Also, face gear 410 and a helical or spur input pinion 420 arestraightforward to mold or cut from plastic or other material withoutrequiring undercuts.

An upper part of face gear 410 as shown in FIGS. 4A and 4B includesseparated plates 416, and plates 416 connect to toothed portion 414 tocreate an arrangement with a “Y” or inverted “h” shape including a gapbetween plates 416. As described further below, the gap between plates416 provides space for instruments components, e.g., cables and pulleysystems, that need access to the instrument shaft. Plates 416 alsoaccommodated connector 430, which may be mounted between plates 416 sothat connector 430 can pivot and keep push-pull element 360 extendingalong the length axis of the instrument shaft. FIG. 5 shows an explodedview of one implementation of connector 430. In the implementation ofFIG. 5, connector 430 includes a swing 510, which may be a stamped metalpiece that snaps into notches in plates 416, and includes a clamp 520that may bolt on to swing 510 to affix on swing 510 a metal grip rod 530that is at the proximal end of push-pull element 360. An electricallyinsulating sheath 540 and an end cap 550 may be provided on grip rod 530to electrically isolate push-pull element 360 from mechanical portionsof the backend of the medical instrument, particularly when the distalgrip mechanism may be electrically energized for cautery purposes.

Connector 430 attaches to face gear 410 at a moment arm or radius thatmay be selected according to the geometry of the instrument backend,e.g., according to a distance X2 between pinion 420 and instrument shaft114. A radius R1 from rotation axis of face gear 410 to connector 430may similarly be selected according to locations of face gear shaft 412and instrument shaft 114. The mechanical advantage that actuationmechanism 400 may provide generally depends on radius R1 at whichconnector 430 attaches to face gear 410, a radius R2 of face gear 410,and a gear ratio between face gear 410 and pinion 420. Since radius R2may be significantly larger than radius R1 and face gear 410 may besignificantly larger than pinion 420, actuation mechanism 400 canachieve a relatively high mechanical advantage so that the mechanicaladvantage for a particular implementation may be selected from a largerange. Implementations of grip actuation mechanisms disclosed herein canprovide many further advantages over prior systems. In particular,actuation mechanism 400 may provide a lower sliding friction than amechanism using worm or crossed helical gears, so that actuationmechanism is back-drivable. In particular, direct movement of a gripmechanism can drive movement of actuation mechanism 400. This allows auser to directly position a grip mechanism of a medical instrumentwithout damaging the medical instrument. Grip actuation mechanism 400also has geometric flexibility as described above to accommodate offsetsand angles between instrument shaft 114 and input spindle 225 since thesection of face gear 410 used and the helix angle of pinion 420 may beadjusted to shift the location and angle of the pinion relative to theaxis of instrument shaft 114.

The configuration of plates 416 of face gear 410 in addition tofacilitating connection of connector 430 and push-pull element 360 toface gear 410 also creates a gap or opening near the top of face gear410, permitting access through face gear 410 to the instrument shaft ofa medical instrument. FIG. 6 schematically shows top and transparentside views of an example of an instrument backend in which the gripactuation mechanism of FIG. 4C is mounted within a chassis 610. In thisimplementation, chassis 610 also contains input spindle 226 with anassociated roll action mechanism (not shown) and contains actuationmechanisms 620 associated with input spindles 221 to 224 that controlcables 622 for actuation of wrists or joints of the instrument. The gapbetween plates 416 shown in FIGS. 4A and 4B allows routing of cables 622between plates 416 to instrument shaft 114 and further provides spacefor pieces of chassis 610 and idler gears 612 that guide cables 622toward instrument shaft 114. Co-filed U.S. Prov. Pat. App. No.62/362,431, entitled “MULTI-CABLE MEDICAL INSTRUMENT,” which isincorporated by reference herein in its entirety, further describescable routing and a multi-piece chassis structure suitable for use withgrip actuation mechanism disclosed herein.

Chassis 610 may hold input spindles 221 to 226 in position forengagement with a docking port on a robotic medical instrument such asdescribed above with reference to FIG. 1. Input spindles 221 to 226 mayeach comprise an input shaft. Chassis 610 also positions manipulator 220for user access and manual rotation of pinion 420, so that a user of amedical instrument may manually open or close the jaws of a medicalinstrument when the medical instrument is in hand instead of beingattached to a robotic system. A user may need to manually open the jawsof a medical instrument, for example, to allow access to the inside andbase of the jaws for cleaning of the jaws. In another case, a user mayneed to install a surgical clip or other medical device in the jaws of amedical instrument before docking the medical instrument on the roboticsystem when the medical instrument is to be used apply the surgical clipor other medical device. A user may also need to manually open the gripsto release a clip or tissue in an emergency when an automated or roboticsystem is non-functional. A problem with manual operation of a gripactuation mechanism is that the torque manually applied through gripactuation mechanism may not be well controlled, and pushing on push-pullelement 360 with too much force may cause element 360 to buckle or kink,thereby damaging the medical instrument. To avoid instrument damage, aslip clutch may be used to connect manipulator 220 to input spindle 225.

FIG. 7A shows an exploded view of one implementation of a manipulator700 with a slip clutch. For the slip clutch of FIG. 7A, a shaft or axle710 of input spindle 225 includes one or more notches 712 that mayreside in a groove 714 around a circumference of axle 710. Axle 710 fitsinto central bore in a knob 720. Knob 720 further has main pieceincluding one or more flexures 722, and the main piece may be shaped formounting of one or more plungers 730, e.g., ball bearings, rollers, orother structures having rounded or angled tips, in or on flexures 722. Aknob cap 724 may fit into the main piece of knob 720 to hold plungers730 in place. Axle 710 when inserted in knob 720 as shown in FIG. 7B maybe positioned so that flexures 722 press plungers 730 into notches 712.Each notch 712 may be sized and shaped to accommodate a portion or a tipof a plunger 730, e.g., less than half, of a spherical surface of aplunger 730. When a user turns the assembled manipulator 700 of FIG. 7B,tips of plungers 730 in notches 712 may apply torque to rotate axle 710with knob 720, but if axle 710 resists rotation, the tips of plungers730 may lift out of notches 712 and slip, e.g., roll along groove 714,when reactive force arising from the torque applied to axle 710overcomes the force with which flexures 722 press plungers 730 intonotches 712. Accordingly, manipulator 700 may slip on axle 710 if thetorque applied through knob 720 is too high.

FIG. 8 shows an alternative implementation of a manipulator 800including a slip clutch that allows a knob 820 to slip on an axle 710when a user applies a large torque through knob 820. Manipulator 800,like manipulator 700 described above, uses plungers 730 that partiallyfit in notches in axle 710, but knob 820 uses springs 830 to pressplungers 730 into the notches. Springs 830 may, for example, be coil orother metal springs. Otherwise, manipulator 800 works in the samefashion as manipulator 700, and the tips of plungers 730 may lift out ofthe notches and slip along the circumference of axle 710 when thereactive force arising from the torque applied through knob 820overcomes the force with which springs 822 press the tips of plungers730 into the notches in axle 710.

FIGS. 9A and 9B respectively show exploded and cross-sectional views ofyet another alternative implementation of a manipulator 900 with a slipclutch. Manipulator 900 may attach to an axle 910 of an input spindle inthe backend of a medical instrument such as disclosed above. Inparticular, axle 910 may be inserted through a bore in a knob insert926, and a plate 912 may be attached to an end of axle 910 below knobinsert 926. FIGS. 9A and 9B illustrate how a pin 914 may be used toattach plate 912 to axle 910 but many other types of attachments couldbe alternatively used. Plate 912 includes one or more notches that aresized to accommodate a tip of a plunger 930. One or more plunger 930 maybe installed with a spring 922 in respective pockets in knob insert 926.A knob cap 924 may clip onto knob insert 926 to hold plate 912 in aposition in which the plunger springs 922 are partly compressed.Manipulator 900 provides a slip clutch that enables manual rotation ofknob cap 924 and axle 910 when the applied torque is insufficient toforce plungers 930 out of the notches in plate 912, but when a greatertorque is applied plungers 930 may slip out of the notches in plate 912so that manipulator 900 slips relative to axle 910.

FIG. 10 shows a manipulator 1000 that attaches an axle 1010 to a knob1020 using a tubular clip 1030 that is friction fit on axle 1010. Clip1030 includes features 1032 that grip into sides of knob 1020 tosecurely hold knob 1020 and clip 1030 together and prevent rotation ofknob 1020 relative to clip 1030. Clip 1030 further includes features1034 that grip axle 1010 to provide the friction fit with some pre-loadso that rotation of knob 1020 rotates axle 1010 as long as the torqueapplied to axle 1010 is insufficient to overcome static friction betweenfeatures 1034 and axle 1010, but knob 1020 slips relative to axle 1010if the applied torque overcomes the friction between clip 1030 and axle1010.

The mechanism described above have primarily been disclosed in thecontext of grip actuation but may be used for actuation of other degreesof freedom in an instrument such as a medical instrument. In particular,some disclosed implementations provide drive or actuation force in bothpulling and pushing directions. While this feature is particularlydesirable for grip motion or actuation, actuation of other types ofinstrument movement may also benefit from use of the mechanismsdisclosed. In addition, although the above examples and otherdiscussions herein often refer to medical procedures and medicalinstruments, the techniques disclosed also apply to non-medicalprocedures and non-medical instruments.

Although particular implementations have been disclosed, theseimplementations are only examples and should not be taken aslimitations. Various adaptations and combinations of features of theimplementations disclosed are within the scope of the following claims.

1. A medical system comprising: a rotatable pinion; a face gear meshedwith the pinion; a medical tool; and a push-pull element comprising aproximal end and a distal end, the proximal end being coupled to theface gear, and the distal end being coupled to the medical tool.
 2. Themedical system of claim 1, wherein a rotation axis of the face gear anda rotation axis of the pinion do not intersect.
 3. The medical system ofclaim 1, wherein the mounting of the pinion couples the pinion to aninput spindle having an engagement feature shaped to engage ateleoperated actuator.
 4. The medical system of claim 1, furthercomprising a slip clutch coupling a manipulator for rotation of thepinion.
 5. The medical system of claim 1, wherein the pinion is selectedfrom a group consisting of a spur gear and a helical gear.
 6. Themedical system of claim 1, wherein the face gear comprises a sectorgear.
 7. The medical system of claim 1, wherein: the face gear comprisesa first plate, a second plate, and a shaft perpendicular to the firstplate and the second plate; and the first plate and the second plate areseparated by a gap through which a second actuation mechanism accessesan instrument shaft of the tool.
 8. The medical system of claim 1,wherein the face gear comprises a first plate, a second plate, and aconnector coupled between the first plate and the second plate, theconnector connecting the push-pull element to the face gear.
 9. Themedical system of claim 1, further comprising a bearing contacting theface gear on a side opposite to where the pinion meshes with the facegear.
 10. The medical system of claim 1, wherein the tool comprises agrip mechanism that is actuated by pushing and pulling the push-pullelement.
 11. The medical system of claim 1, wherein the pinion comprisesa helical gear having a helix angle that accommodates an offset betweenan axis of the pinion and an axis of the face gear.
 12. The medicalsystem of claim 1, wherein the push-pull element couples to the facegear at a first radius from a rotation axis of the face gear, and thepinion meshes with the face gear at a second radius from the rotationaxis of the face gear, the second radius differing from the firstradius.
 13. A medical instrument comprising: a tool; an actuationmechanism coupled to the tool and having an engagement feature shaped toengage an actuator, wherein rotation of the engagement feature actuatesa portion of the tool; and a manipulator coupled to the actuationmechanism and including a slip clutch, wherein rotation of themanipulator actuates the portion of the tool.
 14. The medical instrumentof claim 13, wherein the slip clutch comprises: a plunger; and a springsystem that pushes the plunger into a notch in an axle structure of theactuation mechanism.
 15. The medical instrument of claim 14, wherein:the manipulator comprises a knob; and the spring system comprises aflexure formed in the knob and positioned to push the plunger into thenotch.
 16. The medical instrument of claim 15, wherein: the manipulatorcomprises a knob; and the spring system comprises a spring disposed in apocket in the knob and positioned to push the plunger into the notch.17. The medical instrument of claim 14, wherein the notch is disposed ona cylindrical surface of the axle structure.
 18. The medical instrumentof claim 14, wherein the notch is disposed in a plate that extendsaround an axle of the axle structure.
 19. The medical instrument ofclaim 13, wherein: the manipulator comprises a knob; and the slip clutchcomprises a clip engaged in the knob and providing a friction fit to anaxle in the actuation mechanism.
 20. The medical instrument of claim 13,wherein: the actuator is a drive motor in a robotic system; and themanipulator comprises a manually operated knob.